About the Blood Type Compatibility Calculator
A free, instant blood type tool covering red-cell transfusion compatibility and child blood type prediction — for all eight ABO/Rh types.
What it is
The Blood Type Compatibility Calculator answers two of the most common blood type questions in one place. Select any of the eight standard blood types and it immediately shows which types a donor can give red cells to and which a recipient can receive from, across all ABO groups and Rh factors. Switch to child prediction mode, choose two parents' blood types, and it shows the full set of blood types their child could inherit — based on standard ABO allele combinations and Rh factor rules.
Everything runs entirely in your browser. No data is sent to a server, no account is required, and results appear the moment you make a selection.
Key features
Transfusion compatibility
Select any blood type to see who it can donate to and receive from, for red-cell transfusion. Covers all eight ABO/Rh types with a full compatibility chart for reference.
Universal donor & recipient
O− is the universal red-cell donor; AB+ is the universal recipient. The calculator highlights these automatically when either type is selected.
Child blood type prediction
Enter two parents' blood types to see all possible child blood types, based on ABO allele inheritance (including AA/AO and BB/BO genotype ambiguity) and Rh factor rules.
Reference matrix
A full 8×8 compatibility chart shows all donor/recipient combinations at a glance. It highlights the selected type's row and column for quick cross-referencing, and scrolls horizontally on small screens.
ABO and Rh basics
ABO blood groups
Determined by the antigens on red blood cells. Type O has no A or B antigens. Type A has A antigens. Type B has B antigens. Type AB has both. These antigens determine which types the immune system will attack.
Rh factor
The Rh (Rhesus) antigen is either present (Rh+) or absent (Rh−). Rh+ is dominant — one copy of the allele is enough. Rh− requires two recessive copies. Rh+ donors can only give to Rh+ recipients; Rh− can give to either.
ABO inheritance
A and B alleles are codominant; O is recessive. Each parent passes one allele. A type-A parent may be AA or AO; a type-B parent may be BB or BO. This is why two type-A parents can sometimes have an O-type child.
Educational use only
This tool is for educational purposes only and is not medical advice. Real transfusions and any medical decisions require testing and assessment by qualified healthcare professionals.
Have questions? See the Blood Type Calculator FAQ.
Check blood type compatibility now
Free, no sign-up required. Works on any device.
Open the Blood Type Calculator